This invention relates to a universal joint which while capable of other functions, as is well known in this art, one of its useful functions is to connect two rotating members whose axis of rotation are not coincident. A particular form of such a joint is the universal joint of the prior art composed of spaced hinges, each connected to a rotating member. Examples of such universal joints are those designed to connect the rotor and shaft of a progressive cavity fluid driven motor described in U.S. Pat. Nos. 3,260,069; 3,260,318; 3,894,818; and 3,999,901.
In such combinations, the rotor which is the driving member, traverses a complex path with respect of the driven shaft member (see U.S. Pat. Nos. 3,894,818 and 3,999,901).
One of the problems with such a connection between the rotor and the driven shaft is the length of the connection between the hinges of the universal joint.
As has been pointed out in the prior art, the connecting rod connecting the rotor to the shaft through the universal joint hinges introduces a bending moment to the shaft which presents problems. (see particularly U.S. Pat. No. 3,982,859 and U.S. Pat. No. 4,029,368.)